Muzzle brake

ABSTRACT

A muzzle brake for reducing gun recoil comprises a hollow cylindrical tube (7) having an open forward end and having at least two apertures in the cylinder wall (4) each which is provided with closure means (6) mounted on the tube so as to be movable between a closed position and a fully open position. Each closure means (6) has at least one associated biasing member (22) to bias it into the closed position, which is preferably preloaded to introduce an inertia into the movement of the closure means (6) which is of such a degree that the rapid blast pressure wave passes with little effect, but the longer exhaust wave effects opening. The brake further comprises at least one rearwardly directed gas deflecting surface (13, 30) to deflect the exhaust wave gases rearwards and produce a braking effect.

This invention relates to a muzzle brake for reducing the recoilresulting from the firing of a gun.

Muzzle brakes are used to reduce the recoil experienced by a gun when itis fired. They work by utilizing the forward momentum of the pressurewave produced by expanding exhaust gas which follows the firing of thegun, deflecting some of that exhaust gas rearwards to produce a forwardimpulse on the brake which balances to some degree the recoil impulse onthe gun barrel.

Prior art muzzle brake systems suffer from the disadvantage that theyinteract with the very high pressure short duration blast wave whichoccurs immediately after the projectile has left the muzzle, in additionto the subsequent longer duration exhaust pressure wave produced byexpanding exhaust gases. This blast wave is directed rearwards by themuzzle brake, increasing the blast overpressure in the region behind thegun and exposing the gun crew to increased hazard. The blast is thenfollowed by the exhaust pressure wave which lasts in the order ofmilliseconds.

A standard configuration of muzzle brake comprises a metal blockconnected to the front of the muzzle having an aperture on the insidesurface of the barrel and passages configured to direct exhaust gasesrearwards. Following firing of the gun some of the pressurized exhaustgas escapes through this aperture and is deflected rearwards,attenuating the recoil impulse on the barrel. However, the metal blocktype of brake allows a considerable quantity of exhaust gas to passforward through the muzzle, and thus is relatively inefficient and onlyreduces the recoil force by approximately 50%.

Howitzers normally employ a design of brake which is more effective atreducing recoil. A howitzer style brake includes a structure supportedin front of the muzzle having a larger diameter than that of the barreland partially closed by an annulus defining a rearwardly directedpressure surface at its forward end. Pressurized exhaust gas expandsinto the volume defined by the structure and is deflected rearwardsthrough apertures in the structure by the annulus. The design increasesthe proportion of exhaust gas which is deflected rearwards, and thusincreases the degree to which the recoil impulse is attenuated.

Certain designs of muzzle brake utilise the pressure of the gasesproduced to effect closing of the barrel. FK-A-2,680,235 discloses abrake which has pivoting flaps which close off the barrel and direct thegases through rearwardly directed nozzles. DE-C-0,100,272 discloses adevice which has opening valves in the barrel wall, the opening of thevalves causing a slide to close off the barrel.

The application of muzzle brakes to guns from which saboted projectilesare to be launched also presents problems, as the disruption of theblast pressure wave by the brake can interfere with the sabot discardingprocess. This is particularly true of howitzer type muzzle brakes, whichare found to be entirely unsuitable when launching saboted projectiles.

It is an object of the present invention to provide a muzzle brake forattachment to the muzzle of a gun barrel which minimizes interactionwith the blast pressure wave from the barrel, but which interacts withthe exhaust gas pressure wave by deflecting a significant proportion ofthe exhaust gas rearwards, so as to attenuate the recoil impulse on thebarrel with minimum increase of the blast overpressure in the regionbehind the gun.

Thus according to the invention there is provided a muzzle brakelocatable at the forward end of a gun barrel comprising a hollowcylindrical tube having an open forward end and having at least twoapertures in the cylinder wall, each of the apertures being providedwith associated closure means mounted on the hollow cylindrical tube soas to be movable between a closed position and a fully open positionwherein each of the closure means has at least one associated biasingmember acting on it to bias the closure means into the closed position,said biasing members being preloaded to a predetermined level so as tointroduce an inertia into the movement of the closure means such thatthe gases produced during the blast pressure wave, which immediatelyfollows firing of a gun, pass through the muzzle brake without effectingsignificant opening of the closure means, and at least One surface whichfunctions as a rearwardly directed gas deflecting surface when theclosure means are in an open position.

Consequently, with the closure means in the closed position theapertures in the cylinder wall are sealed so that the cylindrical tubeand the closure means form a sealed pressure surface. In use in thisconfiguration located at the forward end of a gun barrel the muzzlebrake allows gases from the barrel to pass only through its open forwardend. If the closure means are moved from the closed position to an openposition the apertures in the cylinder wall are no longer sealed andgases from the barrel are also able to escape via those apertures.

Each closure means includes at least one biasing member to bias theclosure means in the closed position. The apertures in the cylinder wallare then sealed in the absence of gas overpressure inside the muzzlebrake. If the biasing members are preloaded to a greater degree than maybe necessary to perform a simple closure function this will, inconjunction with the mass of the closure means, introduce an inherentinertia to the opening mechanism. By preloading the biasing members toan appropriate predetermined level it is possible to introducesufficient inertia that when a gun incorporating the device is fired thehigh pressure blast wave, which is of a relatively very short duration,produces only a limited effect on the closure means, and only a minimalescape of gases from the blast pressure wave through the apertures takesplace. The device is thus able to function as an efficient muzzle brakeduring the exhaust gas ejection phase, but allows the blast pressurewave to pass through largely unaffected. The increase in blastoverpressure in the region behind the gun when it is fired and theconsequent problems posed for operators in that area are thus kept to aminimum.

The pressure wave of the exhaust gas ejection phase, being of arelatively much longer duration, overcomes this inertia, causing theclosure means to be moved towards their fully open position whichenables a significant proportion of the exhaust gases to pass throughthe apertures. These can be deflected rearwards by a suitable gasdeflecting arrangement to produce a braking effect which can besignificantly greater than that produced by a simple metal block butwhich unlike howitzer brakes causes little disturbance to the blast waveso that use of the invention with saboted projectiles can becontemplated.

Each of the closure means is preferably mounted so as to rotate about anaxis located between its associated aperture in the cylinder wall andthe forward end of the cylindrical tube. Thus mounted, when the closuremeans are not in the closed position the internal surface of each of theclosure means functions as a pressure surface capable of deflectingrearwards gases from the gun barrel, thereby transferring some of themomentum of those gases rearwards and attenuating the recoil impulse onthe barrel to produce a braking effect.

A more efficient braking effect is achieved however if the muzzle brakeincludes at least one braking member fixedly located towards the forwardend of the cylindrical tube and each having a rearwardly facing brakingsurface configured such that in use the at least one braking surfacecontributes to rearward deflection of gases exiting the muzzle brake viathe apertures.

The braking effect is maximized if a continuous gas deflecting surfaceis provided. Therefore, the muzzle brake preferably includes a singlebraking member having a braking surface providing a rearwardly directedgas deflecting surface which is continuous about the circumference ofthe muzzle brake. Alternatively, if more than one braking member is usedor if a single braking member incorporates discontinuities, for exampleslots to accommodate the function of a mechanism operating the closuremeans, the at least one braking member is preferably so configured as tocombine with the closure means so that the braking surface of the atleast one braking member and the internal surfaces of the closure meanswhen in the fully open position provide a rearwardly directed gasdeflecting surface which is effectively continuous about thecircumference of the muzzle brake.

The simplest form of braking member is an annular disc, presenting aplanar braking surface lying perpendicular to the axis of thecylindrical tube. However, a more efficient braking effect is producedif the rearwardly directed gas deflecting surface is concave.

The rearwardly directed gas deflecting surface is preferablypredominantly frustoconical, with the frustum corresponding to thecircumference of the cylindrical tube. In embodiments of the inventionwhere the gas deflecting surface is configured from a brakingsurface/internal surface of closure means combination a completelyfrustoconical gas deflecting surface is not achievable, but each brakingsurface should comprise a segment of a frustoconical surface, and theclosure means in the fully open position should lie in recesses thereinto provide a continuous and predominantly frustoconical gas deflectingsurface.

The frustoconical gas deflecting surface preferably has a projected apexangle of between 80° and 140°, more preferably between 100° and 120° andmost preferably substantially 110°.

To minimize any lateral impulse from the action of exhaust gases theapertures in the cylinder wall are preferably identical in size andcircumferentially equispaced.

Each closure means is preferably fixed with respect to a shaft, whichshaft is pivotably mounted on the muzzle brake such that its associatedclosure means is movable from the closed position. In this embodiment,each biasing member preferably acts directly on a shaft so as to biasthe closure means into the closed position, and preferably comprises acoil spring or a torsionally mounted helical spring. Each of the closuremeans is preferably provided with a pair of biasing members actingthereon.

Each closure means may be provided with a forward extension and muzzleclosure flap which are so configured that when all the closure means arein the fully open position their respective muzzle closure flapstogether substantially close the forward end of the cylindrical tube,inhibiting the passage of exhaust gases out of the forward end so thatsubstantially all exhaust gases are forced to pass through theapertures. An increased braking impulse is thereby produced.

The muzzle brake is conveniently configured to be attachable to a gunbarrel, in which embodiment the hollow cylindrical tube is provided witha rearward end connectable to the muzzle of a gun. Alternatively, aunitary construction may be provided wherein the hollow cylindrical tubeis continuous with the gun barrel and constitutes the forward sectionthereof.

The invention will now be described by way of example only withreference to FIGS. 1 to 10 which show;

FIG. 1 is a schematic partial cross section of an embodiment of muzzlebrake according to the invention wherein the closure means are in theclosed position;

FIG. 2 is a schematic partial cross section of the muzzle brake shown inFIG. 1 wherein the closure means are in the open position;

FIGS. 3a-3f are schematic illustrations of the operation of the muzzlebrake shown in FIGS. 1 and 2 during a complete cycle of blast andexhaust pressure waves which follows the firing of a gun;

FIG. 4 is a perspective view of an alternative embodiment of muzzlebrake according to the invention;

FIG. 5 is a perspective view of an alternative embodiment of muzzlebrake according to the invention;

FIG. 6 is a perspective view of the muzzle brake shown in FIG. 5 from analternative angle;

FIG. 7 is a perspective view of an alternative embodiment of muzzlebrake according to the invention;

FIG. 8 is a perspective view of the muzzle brake shown in FIG. 7 from analternative angle;

FIG. 9 is a perspective view of an alternative embodiment of muzzlebrake according to the invention;

FIG. 10 is a perspective view of the muzzle brake shown in FIG. 9 froman alternative angle.

A muzzle brake constructed according to an embodiment of the inventionis shown in partial longitudinal cross section in FIGS. 1 and 2 in theclosed and an open configuration respectively. The muzzle brakecomprises a hollow cylindrical tube 2 having two identical arcuateapertures 4 located opposite each other in the cylinder wall. In theclosed configuration (FIG. 1) each aperture 4 is sealed by an arcuateclosure flap 6. Each closure flap 6 has an associated supporting rib 8,pivotably mounted so as to be rotatable about a pivot 10 from the closedconfiguration of FIG. 1 to the open configuration of FIG. 2. Mounted atthe forward end 5 of the cylindrical tube 2 is a braking member 12 whichhas a rearwardly extending portion of increased diameter so as to definea rearwardly directed concave braking surface 14 which is continuousabout the circumference of the muzzle brake except where provision ismade in the form of a slot 15 to accommodate each supporting rib 8 asthe brake moves to an open configuration.

In use the rearward end 7 of the cylindrical tube 2 is attached to thebarrel of a gun. In the closed configuration (FIG. 1) each aperture 4 issealed by its associated closure flap 6, and all exhaust gases from thebarrel pass out of the circular aperture 3 at the forward end 5 of thecylindrical tube 2 in the direction of the arrow 16. In the openconfiguration of FIG. 2 some of the exhaust gases pass through theapertures 4 and are deflected rearwards by the concave braking surface14 in the direction of the arrow 17. The forward impulse thus producedon the braking surface partially attenuates the recoil impulse on thegun producing a braking effect.

The operational cycle of the muzzle brake of FIGS. 1 and 2 isillustrated by FIG. 3 a-f.

FIG. 3a represents the position immediately after the gun is fired. Theclosure flaps 6 and supporting ribs 8 are in the closed position and areretained in that position by spring biasing (not shown in FIG. 3). Thisgives the system an inherent inertia which the high intensity blastpressure wave is of too short a duration to overcome, and the gasesassociated with the blast 18 emerge unhindered through the circularaperture 3 at the forward end 5 of the cylindrical tube 2.

The exhaust gases 20 have an associated pressure wave of relatively muchlonger duration, and this pressure acts on the internal surfaces of theclosure flaps 6 to overcome the inherent inertia of the closure systemand cause the supporting ribs 8 to rotate about the pivots 10 openingthe apertures 4 (FIG. 3b). Some of the exhaust gases 20 can then passthrough the apertures 4 and are deflected rearwards by the internalsurfaces of the closure flaps 6 and the concave braking surface 14 toproduce a braking effect. Under the influence of exhaust gas pressurethe supporting ribs 8 continue to rotate about the pivots 10 until afully open configuration is reached where the closure flaps 6 lie snuglywithin the slots 15 in the braking member 12 so as to produce acircumferentially continuous rearwardly directed gas deflecting surfaceto maximize the braking effect (FIG. 3c).

As the exhaust gas pressure decreases towards the end of the cycle thesupporting ribs 8 rotate back around the pivot 10 under the influence ofthe spring biasing (FIG. 3d, e), so that the muzzle brake returns to thefully closed configuration at the end of the cycle (FIG. 3f).

FIG. 4 illustrates an alternative embodiment of the invention. As withthe previous embodiment, the muzzle brake comprises a hollow cylindricaltube 2 with two identical opposite apertures 4, each having anassociated closure flap 6. For illustration purposes the upper closureflap is represented in the closed and the lower closure flap in a fullyopen position respectively. Mounted towards the forward end of thecylindrical tube 2 is a diametrically recessed annular disc 28 the rearsurface of which constitutes a flat braking surface 30.

Each closure flap 6 is connected to a supporting rib 8 to which isattached a shaft 32. Each end of the shaft 32 is pivotably mountedthrough an aperture within a raised segment 29 of the diametricallyrecessed disc 28, so that its associated closure flap 6 is movable toand from a closed position. Each flap 6 is spring biased into the closedposition by a pair of semi-loop springs each comprising a 2.5 cm widestrip of carbon spring steel 22 mounted between a mounting plate 24 onthe supporting rib 8 and a base plate 26 fixed to the forward surface ofthe diametrically recessed disc 28. Strip thicknesses of the order of0.25 mm-0.4 mm are found to give adequate flexibility with strength andare readily available. Paired springs are preferred as offering greaterreliability in operation.

In use the rearward end 7 of the hollow cylindrical tube 2 is attachedto a muzzle of a gun barrel. As with the previous embodiment, thesprings are of a resilience which produces an aperture closure systemthe inertia of which is such that the blast pressure wave which followsthe firing of the gun is of insufficient duration to cause the apertures4 to be opened significantly and passes through substantiallyunhindered. Under the influence of exhaust gas pressure the supportingribs 8 and shafts 32 pivot opening the apertures 4 to allow exhaustgases to pass through. These are deflected rearwards by the internalsurfaces 13 of the flaps 6 and the braking surface 30 to produce abraking effect as before. Recoil attenuation efficiencies of 70% orhigher can be achieved, offering a significant improvement over simplemetal block brakes. The extent to which a supporting rib 8 can pivot isrestricted by a flap limiter 34, defining a fully open configuration asillustrated by the lower part of FIG. 4.

As gas pressure recedes towards the end of the exhaust phase theresilience of the semi-loop springs 22 cause each flap 6 and itsassociated supporting rib 8 to move back towards the closed position viathe pivoting action of the attached shaft 32. At the end of the exhaustphase the flaps 6 have returned to position so as to fully close thearcuate apertures 4 in the cylindrical tube 2 and the muzzle brake isready for the firing of the next round.

The embodiment illustrated in FIGS. 5 and 6 similarly comprises a hollowcylindrical tube 2 with two identical opposite apertures 4 and closureflaps 6, with the upper closure flap illustrated in the closed and thelower closure flap in the fully open position respectively. Mountedtowards the forward end 5 of the cylindrical tube 2 is a braking member12 which has a rearwardly extending portion of increased diameter so asto define a rearwardly directed concave braking surface 14 and which isslotted in like manner to the equivalent member of the embodiment ofFIGS. 1-3. Other than at the slotted areas the braking surface isfrustoconical, and if notionally projected forwards to an apex wouldoptimally have an apex angle of 110°.

At either side of each slot 15 the braking member 12 is configured toprovide a shaft supporting lug 36 through which a shaft 32 is rotatablymounted. A flap support member 38 is fixedly connected between eachshaft 32 and a closure flap 6 such that the arrangement is pivotableabout the shaft 32 to move the flap 6 to and from a closed position.

Each shaft 32 extends laterally beyond the supporting lugs 36, and astrip of spring steel 40 is attached to and coiled around each lateralextension. Two spring mounting plates 42 are laterally mounted onto thebraking member 12 so as to lie between the lateral extensions of theshaft 32, one to each side of the cylindrical tube 2. Each spring 40 isthen attached to the nearest spring mounting plate 42 in a stressedstate so as to bias its associated shaft, support member and flaparrangement into the closed configuration.

When a gun with this embodiment of muzzle brake attached is fired, thedegree of spring biasing and the mass of shaft 32, support member 38 andclosure flap 6 together provide an inertia to the system which retainseach flap 6 substantially in the closed position during passage of theshort duration blast pressure wave. Exhaust gas pressure overcomes thisinherent inertia to cause the flaps 6 and support members 38 to movefrom the closed position via the pivoting action of the shaft 32 openingthe apertures 4 to allow exhaust gases to pass through. These aredeflected rearwards by the internal surfaces 13 of the flaps 6 and theconcave braking surface 14 to produce a braking effect as before. Withthis embodiment of muzzle brake the extent to which a support member 38can pivot will in practice be restricted, and a fully open positiondefined, by its impact with a flap limiter analogous to members 32 inFIG. 4 but omitted here for clarity. In an arrangement identical to thatshown in these figures the extent to which a support member 38 can pivotwill be restricted by impact of its associated closure flap 6 with thebraking surface 14, which is a less desirable arrangement as distortionof the closure flaps could result. As exhaust gas pressure recedes theflaps 6 return to the closed position under the influence of springbiasing in like manner to the other embodiments.

The embodiment illustrated in FIGS. 7 and 8 is broadly similar to thatillustrated in FIGS. 5 and 6 and like components are labelled with likenumerals. Both figures illustrate the upper closure flap in the closedand the lower closure flap in the fully open position respectively.

This embodiment differs from the embodiment illustrated in FIGS. 5 and 6in that the flap support member 38 includes a forward extension 46 towhich is attached a muzzle closure flap 48. Exhaust gas pressureovercomes the spring biasing to cause the flaps 6 and support members 38to move from the closed position via the pivoting action of the shaft32. The arrangement pivots to a fully open position (as illustrated bythe lower flap, support and shaft arrangement in FIGS. 7 and 8) whereinthe muzzle closure flap 48 attached to the forward extension 46 of eachsupport member 38 covers a semicircular segment of the circular aperture3 at the forward end of the hollow cylindrical tube 2. With both of themuzzle closure flaps 48 in this position the passage of exhaust gasesthrough the aperture 3 is prevented, so that the flow of exhaust gasespassing axially along the centre of the cylindrical tube 2, which wasundeflected in previous embodiments, is diverted back along the tube andpasses through the apertures 4. An enhanced braking effect is therebyproduced. In this position the muzzle closure flap 48 also limits theextent of rotation of the shaft, support and flap arrangement, therebyperforming an equivalent function to the flap limiter in previousembodiments (34 on FIG. 4). As exhaust gas pressure recedes the flaps 6return to the closed position under the influence of spring biasing inlike manner to the other embodiments.

The muzzle brake illustrated in FIGS. 9 and 10 shows alternative springbiasing means incorporated into a similar muzzle brake arrangement tothose of FIGS. 5 to 8 and like components are labelled with likenumerals. In this embodiment the muzzle brake is structurally continuouswith the barrel of a gun. Apertures 4 are located towards the forwardend of a gun barrel 54, and the remaining components are mountedthereon.

The four coiled strips of spring steel which constituted the biasingmembers of FIGS. 5-8 are replaced by four torsionally mounted helicalsprings 50. The braking member 12 is mounted on the gun barrel 54forward of the apertures 4 and has a forward part configured to providefour spring mounting lugs 52. Each helical spring 50 is locatedcoaxially around a lateral extension of a shaft 32 and is fixedlymounted between a spring mounting lug 52 and a forward extension 46 of aflap support member 38 in a torsionally stressed state so as to bias itsassociated shaft, support member and flap arrangement into the closedconfiguration. When the gun is fired the braking function is effected inlike manner to earlier embodiments.

I claim:
 1. A muzzle brake locatable at the forward end of a gun barrelwhich, when fired, provides a relatively short duration blast pressurewave followed by a relatively longer duration exhaust pressure wave,comprising:a hollow cylindrical tube having an open forward end andhaving at least two apertures in the cylinder wall, each of theapertures being provided with associated closure means mounted on thehollow cylindrical tube so as to be movable between a closed positionand a fully open position wherein each of the closure means has at leastone associated biasing member acting on the closure means to bias theclosure means into the closed position, said biasing members beingpreloaded to a predetermined level so as to introduce an inertia intothe movement of the closure means such that the gases produced duringthe blast pressure wave, which immediately follows firing of a gun, passthrough the muzzle brake without effecting significant opening of theclosure means and permitting opening of the closure means during saidexhaust pressure wave, and at least one surface which functions as arearwardly directed gas deflecting surface when the closure means are inan open position.
 2. A muzzle brake locatable at the forward end of agun barrel comprising:a hollow cylindrical tube having an open forwardend and having at least two apertures in the cylinder wall, each of theapertures being provided with associated closure means mounted on thehollow cylindrical tube so as to be movable between a closed positionand a fully open position wherein each of the closure means has at leastone associated biasing member acting on the closure means to bias theclosure means into the closed position, said biasing members beingpreloaded to a predetermined level so as to introduce an inertia intothe movement of the closure means such that the gases produced duringthe blast pressure wave, which immediately follows firing of a gun, passthrough the muzzle brake without effecting significant opening of theclosure means, and at least one surface which functions as a rearwardlydirected gas deflecting surface when the closure means are in an openposition wherein each of the closure means is mounted so as to rotateabout an axis located between its associated aperture in the cylinderwall and the forward end of the cylindrical tube.
 3. A muzzle brakelocatable at the forward end of a gun barrel comprising:a hollowcylindrical tube having an open forward end and having at least twoapertures in the cylinder wall, each of the apertures being providedwith associated closure means mounted on the hollow cylindrical tube soas to be movable between a closed position and a fully open positionwherein each of the closure means has at least one associated biasingmember acting on the closure means to bias the closure means into theclosed position, said biasing members being preloaded to a predeterminedlevel so as to introduce an inertia into the movement of the closuremeans such that the gases produced during the blast pressure wave, whichimmediately follows firing of a gun, pass through the muzzle brakewithout effecting significant opening of the closure means, and at leastone surface which functions as a rearwardly directed gas deflectingsurface when the closure means are in an open position, furthercomprising at least one braking member fixedly located towards theforward end of the cylindrical tube and having a rearwardly facingbraking surface configured such that in use the at least one brakingsurface contributes to rearward deflection of gases exiting the muzzlebrake via the apertures.
 4. A muzzle brake according to claim 3comprising a single braking member having a rearwardly facing brakingsurface providing a rearwardly directed gas deflecting surface which iscontinuous about the circumference of the muzzle brake.
 5. A muzzlebrake according to claim 3 wherein the at least one braking member is soconfigured as to combine with the closure means so that the brakingsurface of the at least one braking member and the internal surfaces ofthe closure means when in the fully open position provide a rearwardlydirected gas deflecting surface which is effectively continuous aboutthe circumference of the muzzle brake.
 6. A muzzle brake according toclaim 4 wherein the rearwardly directed gas deflecting surface isconcave.
 7. A muzzle brake according to claim 6 wherein the gasdeflecting surface is predominantly frustoconical.
 8. A muzzle brakeaccording to claim 7 wherein the frustoconical gas deflecting surfacehas a projected apex angle of between 80° and 140°.
 9. A muzzle brakeaccording to claim 8 wherein the projected apex angle is between 100°and 120°.
 10. A muzzle brake according to claim 1 wherein the aperturesin the cylinder wall are identical in size and circumferentiallyequispaced.
 11. A muzzle brake according to claim 10 wherein theapertures are arcuate.
 12. A muzzle brake according to claim 1 whereineach closure means is fixed with respect to a shaft, which shaft ispivotably mounted on the muzzle brake such that its associated closuremeans is movable between a closed position and a fully open position.13. A muzzle brake according to claim 1 wherein each biasing membercomprises a semi-loop spring.
 14. A muzzle brake according to claim 12wherein each biasing member acts directly on a shaft.
 15. A muzzle brakeaccording to claim 14 wherein each biasing member comprises a coilspring.
 16. A muzzle brake according to claim 14 wherein each biasingmember comprises a torsionally mounted helical spring.
 17. A muzzlebrake locatable at the forward end of a gun barrel comprising:a hollowcylindrical tube having an open forward end and having at least twoapertures in the cylinder wall, each of the apertures being providedwith associated closure means mounted on the hollow cylindrical tube soas to be movable between a closed position and a fully open positionwherein each of the closure means has at least one associated biasingmember acting on the closure means to bias the closure means into theclosed position, said biasing members being preloaded to a predeterminedlevel so as to introduce an inertia into the movement of the closuremeans such that the gases produced during the blast pressure wave, whichimmediately follows firing of a gun, pass through the muzzle brakewithout effecting significant opening of the closure means, and at leastone surface which functions as a rearwardly directed gas deflectingsurface when the closure means are in an open position, wherein eachclosure means is provided with a forward extension and muzzle closureflap which are so configured that when all the closure means are in thefully open position their respective muzzle closure flaps togethersubstantially close the forward end of the cylindrical tube.
 18. Amuzzle brake according to claim 1 wherein the hollow cylindrical tubehas a rearward end connectable to the muzzle of a gun.